Quenching oil



Patented Apr. 28, 1925.

UNITED STATES eaten orrt HUGH RODMAN, OF OAKMONT, AND EARL E. BOREN,

lit-a 0 OF PENN TOWNSHIP, ALLE- GI-IENY COUNTY, PENNSYLVANIA, ASSIGNOI 3TO RODMAN CHEMICAL GOMPANY, 0F VERONA, PENNSYLVANIA, A CORPORATION OFPENNSYLVANIA.

ennncnrne OIL.

No Drawing.

To all whom it may camera:

Be it known that we, HUor-r RODMAN and EARL E. BOREN, citizens of theUnited States, and residents of Oakmontand Penn Township, respectively,in the county of Allegheny and State of Pennsylvania, have invented anew and useful Improvement in Quenching Oil, of which the following is aspecification.

This invention relates to oils to be used for quenching steel.Itcomprises the discovery that certain oilsof low viscosity and lowflash-point may have their initial quenching speed materially increasedby adding thereto a comparatively small proportion of oil of highflash-point and high viscosity.

The principal object of the invention is the production of a low-costquenching oil, of low viscosity and very rapid initial quenching speed.It is also an object to increase the initial quenching speed of anordinary low viscosity mineral quenching oil, without materially raisingits viscosity, and Without materially increasing the cost. Anotherobject is to produce an oil having a comparatively high' initialquenchingspeed for the upper range of temperatures of the articles to bequenched, but retaining the valuable quenching characteristics of oilsas compared to other liquids. in the matter of slow quenching at lowertemperatures of the steel.

Other objects and advantages will be apparent tothosefamiliar with theart from the following specification.

In the heat treatment of steel, oil baths are used for two purposes. Redhot steel is immersed in comparatively cool oil to secure a rapidcooling of the steel and thereby to harden it in Well known manner. Thisis known as quenching. After the steel has'been cooled by this quenchingprocess it is sometimes reheate' by immersing it in highly heated oil,for the purpose of reducing the extreme hardness produced by thequenching process. Oil used in the cooling process is called thequenching bath and that used in the second or reheating step is calledthe temperiiig bath.

The quenching bath usually consists of-a mineral oil having a viscositynot over 150 seconds measured at 100 upon the Sayb-olt viscosimeter, anda'flash-point of 300 to Application filed November 19, 1923. Serial No.675,500.

450 measured by the Cleveland open cup method. (Throughout thisspecification degrees of temperature refer to the Fahrenheit scale.) Thetempering bath generally consists of a mineral oil having a flashpointover 550 and a viscosity of 150 or more at 212. The art has generallyused as a quenching bath an oil having low viscosity, which implies anoil of cornparatively low-flash point. Oil of low viscosity is so usedbecause less of such oil adheres to the steel parts upon removal fromthe bath,-there being therefore less Waste from drippagc, and becauseoils of low viscosity are believed to give more rapid cooling of thesteel than those of high viscosity. Tempering baths must necessarily beheated to a very high temperature for tempering steel. There-fore. oilsfor this purpose must have a high fiaslrpoint, which implies theadditional characteristics of high viscosity.

lVater quenches hot steel much more rapidly than oil. In fact thequenching time of water is only about one-third that of the oilscommonly used. Or, stated another Way, the heat absorption by water fromred hot steel is about three times as rapid as the heat absorption bythe quenching oils generally used. But oil as a quenching bath has thevaluable property or characteristic of cooling the steel very slowlyafter the steel has been reduced in temperature to say 700 to 600.quenching characteristic of maintaining a substantially uniform initialquenching speed over a wide range in temperature variation of thequenching bath itself.

There have been many efforts made ,to produce an oil of more rapidinitial quenching speed, while at the sametime preserving the valuableoil quenching-characteristics just referred to, and keeping the cost ofthe oil withinv a practical commercial range. Some increase in quenchingspeed has been attained by adding to the usual low'viscosity mineralquenching oil a small amount of an animal oil, as lard or. degras, oreven some of the vegetable oils. This mixture has resulted in aquenching bath of somewhat greater initial quenching speed than themineral oil alone, but this increase has been small as compared to thatattained by our product described, and the added animal or vegetableoils are expensive.

Oil also has the desirable We have discovered that the initial uenchinrate of mineral oils of certain c iaracterist-ics may be reatlyincreased by the addition of a smal pro ortion of another mineral oil ofwidely different characteristics, and apparently this change is in someway connected with the respect1\ze flash-points or viscosities of the0115 that are combined.

We have discovered that a product comprising a low-flash, low-viscositymineral oilcombined with a smaller amount of a comparativel high-flash,high-viscosity mineral oil, ias an initial quenching speed much morerapid than that of either of the constituent oils separately.Specifically, we have discovered that an ordinary low-flashlow-viscosity mineral quenching oil may have its initial power to absorbheat from red hot steel, that is to say its rapidity of quenching athigh temperatures, greatly in creased by the addition to'it of a smallproportion of a high flash-point'mineral oil, while the viscosity of theresultant product is only slightly raised by the added 011. Perhaps itwould be more accurate to say that we have discovered that when aproduct is made by adding to an ordinary lowfiash, low-viscosity mineraloil, a small amount of a high-flash, high-viscosity mineral oil, theinitial quenching speed of the resultant product is much greater thanthat of the low-flash, low-viscosity oil alone. The hi h-fiash oil hasviscosity and flashpoint ciaracteristics which render it aloneunsuitable and undesirable as a quenching bath.

A specific example of a product involving this invention and tested andused by us with markedly successful and improved results was made byadding to an ordinary quenching oil consisting of 100 parts of aPennsylvania neutral oil having a viscosity of about seventy seconds at100 and a flash-point of'about 350, about ten parts of a heavy residuumoil derived from Pennsylvania crudes, having a flash-point of about 020and a viscosity of about 200 seconds at 212. These very high flash oilsare known in the trade as Steam refined oils, the expression meaningthat the distillation of the petroleum has been carried on in thepresence of steam, in order to minimize the production of tar, whichwould otherwise be formed at the high distillation temperaturesnecessary to produce oils of this character. These steam refined oilshaving a flash-point of approximately 620 are the residuums left in thestill after as much oil as possible has been distilled off, without theformation of tar or asphaltum. Such an oil is of a consistency similarto very thick molasses. We believe no one has hitherto made use of theseoils as a quenching bat-h or as an ingredient 0 a quenching bath, and wefind that the additlon of a small amount of such heavy, high-flash oil,will materially raise the quenching rate of the low-viscosity lowflash-point mineral oil.

' We have found by careful measurements that such a mixture or productof mineral oils will quench red hot steel from about 1500 down to about1200", in less than half the time required by any commercial quenchingoil which we have been able to find upon the market. At the same time,

we have determined by careful mea-surements that this product retainsthe desired characteristics of oil as a quenching medium in the way ofvery slow quenching after the steel has been reduced to about 700, and

also that the mixture maintains a substantiall uniform initial quenchingspeed regar less of variations in the temperature of the oil itself. Wehave been able with such a product as that described to reduce thequenching time required in cooling steel from a red hot to a nearlyblack heat to about one-half that of any previously known oil. Or,stated another way we have succeeded in increasing the initial quenchingrate of oil baths for red hot steel from about one-third the quenchingrate of water to more than two-thirds the quenching rate of water, thuscarrying ordinary red hot steel through its critical points at abouttwice the quenching speed of the oils ordinarily used. This is about therate of quenching most desired for commercial work. At the same time wehave found that such a quenching oil retains unimpaired the desirableoil-characteristics for quenching baths above referred to. In addition,our product retains the low-viscosity property of the light oil.

When we refer to initial quenching rate of oil we mean the first coolingof the steel from its red hot state, say l500, down to about 700 or(500. The rate is much faster with oils during this initial stage thanthereafter. In effect oil in quenching has a sort of cushioning effect,producing a comparatively rapid drop of temperature at first, butslowing up the cooling at the end;

while water cools the steel with substantially uniform rapidity down tothe temperature of the water itself. It is this slower final coolingthat toughens the steel and this characteristic of oil is one of itsmost valuable functions in a quenching bath. Our product has a much morerapid initial cooling than oils heretofore used, but below 600 thequenching speed drops to substantially the same rate as that of the baseor light oil alone.

We have found that apparently no valuable increase in the quenching rateof the resultant product is secured unless the fproduct comprises oilwhich alone would.

have a flash-point above 450. In fact we think the quenching speed of.the product is materially increased only when an oil having aflash-point above 475 is comprised. The rapidity of quenching action ofthe product appears to increase as the flashpoint of the heavyingredient increases, u

to about 620 flash-point, which is approximately the highest flash-pointwe have found in commercially available oils. found that the initialquenching speed of the product secured by adding to a lowflash oil amineral oil of a flash-point of 500 is only about two-thirds thatsecured by adding to a similar oil an equal proportion of a mineral oilhaving a flash-point of about 620. Our experiments also lead us toconclude that the presence of any oil of intermediate flash-point valueis undesirable. The presence of oil of intermediate flash-point does notappear to increase the resultant quenching speed, While suchintermediate oil does raise the viscosity of the tively high bath, whichis undesirable. Therefore the preferred product comprises a mineral oilof low viscosity and flaslrpoint, in combination with a small amount ofmineral oil of very high flash-point.

Furthermore, we have found that while the initial quenching rate of theproduct appears to increase with the flash-point of the heavy oil(provided the flash-point of the latter is high) it does not appear toincrease with the volume of the high-flash constituent oil after theproportion of the latter reaches about ten percent of the low-flash oil.We have experimented with many different oils, and find that resultsvary somewhat according to the character of the particular oils used,but that in general about ten percent ot a high flash-point,high-viscosity oilwith the remainder a low-flash, low-viscosity oil,free from oil of intermediate flash-point and viscosity values, givesthe best results.

From these observations we conclude that the best form of our inventionis a quenching oil comprising a base or body of mineral oil ofcomparatively low viscosity and low flash-point. and about ten percentof a heavier mineral oil, of high viscosity and high flash-point, andthat preferably the product should be free from oils of intermediateviscosity or flash-test characteristics. Such oils of intermediateproperties do not increase the quenching speed of the oil, but on theother hand have the bad eil'ect of increasing the viscosity of themixture, which, as above pointed out is undesirable for commercialreasons.

, We claim:

1. A quenching oil comprising a low flash-point mineral oil, incombination with a lesser amount of a mineral oil of comparatlash-point.A quenching oil comprising a low We have comprising two mineral oils ofwidely ditferent respective flash-points.

5. A. quenching oil of low viscosity comprising two mineral oils ofwidely different respective viscosities.

6. A quenching oil comprising a mineral oil of low viscosity and lowflash-point .combined with a lesser amount of a mineral oil ofcomparatively high viscosity and high flash-point, and substantiallyfree from mineral oils of intermediate viscosity and flash-pointcharacteristics.

7. A quenching oil of low viscosity and low flash-point, comprisin amineral oil of low flash-point in com ination with a smaller amount ofmineral oil of comparatively high flash-point, the product beingsubstantially free from oils of intermediate flash-pointcharacteristics.

8. A quenching oil of low viscosity. comprising a mineral oil of lowviscosity in combination with a mineral oil of high. viscosity, theproduct being substantially free from oils of intermediate viscositycharacteristics.

9. A quenching oil comprising in combination about one hundred parts byvolume of a mineral oil having low-viscosity and low flash-pointproperties and about ten. parts of a mineral oil having flash-point andviscosity properties high in comparison to the first mentioned oil.

10. A quenching oil comprising a mineral oil having a flash-point ofless than 450 combined with a lesser amount of a mineral oil having aflash-point of over 500,

11. A quenching oil comprising a mineral 'oil of a flash-point ofapproximately 350.

with a lesser amount of a mineral oil having a flash-point of over 500.

14. A quenching oil comprising a lowviscosity, low flash-point mineraloil and a smaller amount of a high flash-point steamrefined oil.

15. A quenching oil of low viscosity and low flash-point, consisting ofa low-viscosity,

of mineral oil.

viscosity mineral oil, consisting in adding thereto a smaller amount ofm1neral 011 of a comparatively high viscosity.

In testimony whereof, we hereunto sign our names' HUGH RODMAN. EARL E.BOREN.

Witness to both signatures: W. '1. DIBLE.

